Acanthaceae are a large tropical family with numerous species grown as ornamentals. Representatives of the two largest genera barely reach southern Michigan, where all three species are quite rare.
1. Leaves ca. 7–15 times as long as broad, completely glabrous; calyx and stems glabrous; corolla bilaterally symmetrical, less than 1.5 cm long, the lobes about as long as the tube or longer; stamens 2.
1. Leaves less than 3.5 times as long as broad, with at least minute strigose pubescence; calyx and stem pubescent; corolla (except on cleistogamous flowers) nearly regular, ca. 3–7 cm long, the lobes much shorter than the tube; stamens 4.
All species found in Acanthaceae
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. March 22, 2019. https://www.michiganflora.net/family.aspx?id=ACANTHACEAE.